This invention relates to an electric component with a soldering-less terminal structure, and more particularly to an electric component with a terminal connection structure which permits connection without soldering.
Use of freon (flon) is subject to restriction in view of environmental pollution, so that it is highly required to connect a terminal conductor, a lead wire or the like to a connection electrode of a circuit board without soldering. This is likewise true of an electric component called a focus pack used for adjustment of a focus voltage of a cathode ray tube (CRT), a screen voltage thereof or the like.
U.S. Pat. No. 4,471,339 discloses a high-voltage variable resistor unit including a terminal connection structure for connecting, by means of a terminal fitment like a coiled spring provided at one end thereof with a ring into which a connection conductor or connection terminal is inserted, a connection electrode of the resistor unit to the connection terminal without soldering. Such a conventional terminal fitment as taught in the U.S. patent fails to firmly hold the connection terminal therein, to thereby cause the connection terminal to be readily released from the terminal fitment. Also, it tends to cause a failure in electric connection between the connection terminal and the terminal fitment. Further, the above-described construction of the terminal fitment requires to keep the connection terminal and connection electrode connected together prior to incorporation of a circuit board in an insulating casing. This, when use of a lead wire of an increased length is required for the connection conductor, causes the long lead wire to obstruct assembling of the high-voltage variable resistor unit. In particular, when the high-voltage variable resistor unit including the terminal connection structure is combined with a fly-back transformer, the high-voltage variable resistor must be placed in a heating oven together with the long lead wire for the purpose of subjecting a resin material for molding of the fly-back transformer to heat curing. Unfortunately, the long lead wire renders the operation highly troublesome, leading to a deterioration in production efficiency.
Also, U.S. Pat. No. 5,546,280, which corresponds to Japanese Patent Application Laid-Open Publication No. 318669/1994, owned by the assignee discloses two kinds of terminal connection structures for connecting a core wire of a lead to a connection electrode of a circuit board without soldering. FIG. 9 of the U.S. patent shows a connection structure using a plurality of terminal assemblies in each of which a terminal fitment provided with a conductor holding section for interposedly holding the core wire of the lead and a conductive rubber member are combined together. The conductive rubber member is used as a connection means for connecting a terminal fitment and a connection electrode arranged on a circuit board 1 to each other without soldering. Unfortunately, a conductive rubber material for the conductive rubber member incorporated in such construction of the U.S. patent is inherently expensive, to thereby cause an electric component or a high-voltage electric component such as a high-voltage variable resistor unit having the conductive rubber member incorporated therein to be disadvantageously increased in cost. Also, the conductive rubber member is formed by cutting an elongated linear conductive rubber material, to thereby be varied in length. Also, the conductive rubber material exhibits excessively increased elasticity. Thus, arrangement of the plural terminal assemblies often causes mounting of the electric component to be carried out while keeping the circuit board inclined due to both a variation in length of the conductive rubber members and increased elasticity thereof, to thereby render assembling of the electric component highly troublesome.
U.S. Pat. No. 5,546,280 also discloses a connection structure including a terminal fitment in which a conductor interposing or holding section and a contact terminal section exhibiting elasticity are integrally incorporated. The terminal fitment is so constructed that the elastic contact terminal section functions to connect the conductor holding section and an electrode on a circuit board to each other without soldering. Also, the U.S. patent discloses a structure for connecting a plurality of electrodes arranged on the circuit board and a plurality of connection conductors to each other without soldering, respectively. Further, the U.S. patent discloses a high-voltage variable resistor unit having the terminal fitment of such an integral type incorporated therein and constructed in such a manner that a lid member covers a board receiving chamber of an insulating casing.
In addition, U.S. Pat. No. 5,546,280 described above and U.S. Pat. No. 5,508,678 likewise owned by the assignee each disclose a terminal fitment which includes a conductor holding section for interposedly holding a connection conductor, wherein the conductor holding section is provided with a plurality of edges adapted to bite into an end of the connection conductor when drawing force is applied to the connection conductor.
The above-described terminal fitment having the conductor holding section and contact terminal section integrally incorporated therein which was proposed by the assignee is significantly reduced in the number of parts, resulting in being highly advantageous when automatic assembling of the terminal fitment is accomplished with increased accuracy. However, incorporation of the terminal fitment of the integral type into the insulating casing by manual operation causes assembling of the electric component to be deteriorated in accuracy, so that the terminal fitment is incorporated in the electrical component while being inclined. This causes a pressure of contact between the contact terminal section exhibiting elasticity and the electrode on the circuit board to be reduced, resulting in a failure in contact therebetween rarely occurring.
Also, the conventional terminal fitment wherein the conductor holding section is provided with a plurality of the edges adapted to bite into the end of the connection conductor when drawing force is applied to the connection conductor does not cause any problem so long as only the drawing force is applied thereto. However, it encounters a problem that the connection conductor is cut by the edges of the conductor holding section in the worst case, when turning force which tends to cause turning of the connection conductor about a central axis thereof is repeatedly applied to the connection conductor or the connection conductor is formed into a thin configuration.